Circuit-protecting apparatus.



J. G. ZIMMERMAN.

cmcun PROTECTING APPARATUS.

APPLICATION FILED MAY 17, 1912.

Patented. Apr. 24, 1917.

UNITED STATES PATENT OFFICE.

JAMES GFZIMMERMAN, F MILWAUKEE, WISCONSIN, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO ALLIS-CHALMERS MANUFACTURING COMPANY, A CORPORATION OFDELAWARE.

CIRCUIT-PROTECTING APPARATUS.

Specification of Letters Patent. Patented Apr. 24, 1917.

Application filed May 17, 1912. Serial No. 697,892.

To all whom it may concern:

Be it known that I, JAMES G. ZIMMnR- MAN, a citizen of the UnitedStates, residing at Milwaukee, in the county of Mulwaukee and State ofWisconsin, have invented' certain new and useful Improvements inCircuit-Protecting Apparatus, of which the following isv a full, clear,and exact specification.

This invention relates to circuit protecting apparatus.

It 'is a known fact that caused to flow through a conducting liquid,such as mercury, for example, there is a tendency for the liquid-todecrease in cross section, thereby causing the current density andresistance of the liquid to increase. This decrease in cross sectionalarea of such conducting liquid varies in the same sense as the strengthof the current passing through the conducting liquid. This means thatthe greater the value of current passing through the liquid, the greaterwill be the tendency of the liquid to decrease in cross sectional area.The cross sectional area of the conducting liquid does not decrease thesame amount along its whole length, however. The greatest decrease incross sectional area occurs at the so-called weakest part of the liquid.This decrease in cross sectional area of the conductin liquid at itsweakest part or section cause by the .passage of current is-Imown as'thepinch effect. When the current has reached a redetermined value thepinch effect may e so great as to reduce the cross sectional area at theweakest point to nothing, thereby breaking the electric circuit of whichthe conducting fluid forms a part. With an increase in the pinch efi'ectthere is an increase indensity and resistance and a correspondingincrease in the potential difference between points on opposite sides ofthe section of the circuit at which the inch efi'ect takes place. In

.view of the act that the pinch effect increases with increase ofcurrent flow and that time is required after a flow of such current toestablish the pinch effect, a time element is introduced. I have takenadvantage of these facts and have so connected current conducting liquidwith respect to a safety operative device that the motor or other deviceto be protected will be cut off "from its source of supply upon theoccurrence of abnormal circuit conditions.

The object of my invention is therefore to provide circuit controllingand protective means adapted to meet the requirements of successfulcommercial operation.

The invention is illustrated in theaccompanylng sheet of drawings,in'which Figure 1 is a diagrammatic view of a system includ-- ing amotor, a circuit-breaker therefor, and means mcludlng a fiuld currentconducting body which is responsive -1n a manner to I current passingtherethrough to cause an if a current is operation of saidcircuit-breaker upon the occurrence of abnormal circuit conditions;

Figs. 2 and 3 are front and end longitudinal'sectional viewsrespectively of a receptacle containing a liquid current conducting bodyillustrating the so-called pinch effect caused by a passage of currentthrough said liquid;

Fig. 4 is a longitudinal sectional view of a vertically arrangedreceptacle containing a liquid capable of producing the pinch ef-- feet;and,

Fig. 5 illustrates the same receptacle as shown in Fig. 4 containing theliquid with the current passing therethrough, showing The various novelfeatures of my invention will be apparent from the description anddrawings, and will be particularly set forth' in the appended claims.

There are a great many different types of apparatus for controlling andprotecting electrical circuits. These various types may be connected insystemsof different description. A particular type of circuitprotectingmeans which I-have found to be effective is one in which Imake use of the soca-lled pinch effect. For the sake of illustration, Iam showing this circuit protecting means as connected in the secondarycircuit of an induction motor, the pinch effect means being adapted tocause the actuation of a device or devices for cutting off the inductionmotor from its source of supply.

"This induction -motor 10 is connected to a supply circuit 11 by leads12 through a circuit-breaker 13, which is normally held in closedposition by a spring 14, but which is adapted to be opened to disconnectthe in- 105 cuit with a current transformer 16 which re- 110 ceivescurrent directly from the main line 11. This circuit is adapted to beclosed by the armature member 17 of a magnet 18 having a coil 19connected in the secondary circonducting body and coil 19' of magnet 18is a resistance 26 which may or may not be included in the circuit.

With the circuit-breaker 13 in closed position current flows into theprimary circuit of the induction motor 10, and a current is induced toflow in the secondary circuit 20 of such induction motor, causingcurrent not only to flow through the adjustable resistance 21 but alsothrough the liquid conducting body 22, resistance 26, and the coil 19 ofmagnet 18-.'.The current passing through the liquid current conductingbody 22 causes said liquid to be agitated in a manner whereby the crosssectional area of the liquid at some point is caused to decrease. With adecrease in the cross sectional area of said liquid, there is anincrease in the density and a corresponding increase in resistance anddrop of Voltage across that section of the liquid conducting body. Withan increase of current there is a greater decrease in the crosssectional area at a certain place of the liquid conducting body, theplace at which this decrease in cross sectional area occurs being theso-called weakest point of the liquid. When the current has risen to acertain predetermined value the cross sectional area at the weakestpoint of the liquid conducting body may be decreased to nothing. Inother words, the circuit may be broken at that point. This decrease inthe cross sectionalv area of the liquid conducting body due to thepassage of the current therethrough is known as the pinch efl'ect. Thegreater the pinch effect the greater will be the density, resistance,and corresponding drop in voltage across said liquid conducting body.The coil 19 of the magnet being in parallel with the liquid conductingbody 22 has the same voltage across its terminals. Current passingthrough the coil under'normal operating conditions would not besufficiently strong to attract the armature 17 to overcome the action ofspring 27 to complete at contacts 28 the circuit containing the currenttransformer 16 and coil 15. But when the voltage 'across terminals ofthe liquid conducting body .22 has increased a predetermined amount, dueto the pinch etfect caused by the current passing through said liquid,the coil 19 will be energized to the extent that the armature 17 will-beattracted into closed position whereby the coil 15 will be energized bycurrent from the current transformer 16 overcoming the action of springl4fcausing the circuit-breaker 13 to open and cutting off inductionmotor 10 from its source of supply. The resistance 26, which isconnected'in parallel with the liquid conducting body 22 and coil 19, is

for the purpose of preventing any sparking one is a vertically arrangedreceptacle con- .talmng current conducting liquid which is capable ofproducing the pinch effect caused by the passing of current through.said liquid. This vertically arranged receptacle 29 is provided with amember 30 having holes 31 to permit the passage of liquid which iscaused to flow upwardly due to the pinch effect. The restricted openingsor holes 31 assist in producing the desired degree of retardation.Passing through this member 30 isone terminal 32, the other terminal 33,being shown as passing through the bottom of the receptacle 29.Receptacles of various shapes and arrangements may be used aslong as theliquid within said receptacles is capable of'producing the so-calledpinch eflect in response to current passing through said liquid. It isnotnecessary that mercury be used, for I other conducting liquids arealso capable of producing the pinch effect. Neither do I limit myself tothe use of liquids, for there may be various elements included in theterm fluids which are capable of producing a pinch efl'ect.. The fiuidcurrent conducting medium may be connected in any circuit in whichcurrent fiows.-

There may also be various modifications and arrangements other than thathere particularly shown and described, and it is my intention to coverall such modifications and arrangements which do not involve a departurefrom the spirit and scope of my invention as set forth in the appendedclaims.

What I claim as new is:

. 1. In combination, an electrical circuit, andcontrolling means forsaid circuit comprising an electro-magnetically "actuated element andmeans comprising a liquid conductor in circuit with the actuating winding of said element for controlling the actuation of said element, saidelement being actuated on the passage of current of a certain valuethrough said liquid conductor.

2. In combination, a circuit including a liquid the cross sectional areaof which varies in response to abnormal circuit conditions, anothercircuit in which the current varies in response to changes in saidliquid, and a circuit controlling device in said last mentioned circuitresponsive to said current variation.

3. In combination, a circuit including a liquid the cross sectional areaof which va-' ries in response to abnormal circuit conditions, a branchcircuit in which the current varies in response to changes in saidliquid, and a circuit controlling device in said last mentioned circuitresponsive to said current variation.

4. In combination, an. electrical circuit, electro-magnetically actuatedmeans for controlling said circuit, and means connected in parallel withthe actuating winding of said controlling means for producing a pincheflect in response to a characteristic of the current in the circuit tobe controlled to cause operation of said controlling means.

5. In combination, an electrically operated member, and a circuitincluding a liquid conductor connected in parallel with the operatingcircuit of said electrically operated member, means for supplyingcurrent to said circuits, said liquid conductor being adapted to beagitated by current variation therein to cause the actuation of saidelectrically operated member. 7

6. In combination, an electromagnetically actuated controllingdevice,iand a circuit in cluding a liquid conductor connected inparallel with the circuit of the actuating winding of said controllingdevice, said liquid conductor being capable of and free to appreciablychange the cross-sectional area of a portion thereof on the flow ofcurrent of a certain value therethrough for a time interval ofappreciable and substantial duration.

'7. In combination, an electromagnetically actuated controlling device,and means for causing operation of said device, said operating meanscomprising a liquid conductor connected in circuit with the actuatingwinding of said controlling means for producing a pinch efiect on theflow of current of a certain value. the increase in the current in saidactuatin winding bein greater than that in said liquid conductor on theoccurrence of said pinch eifect, and the actuation of said controllingdevice being assisted by the proportionally greater increase in thecurrent in said actuating winding than in the current in said liquidconductor.

In testimony whereof I afiix my signature, in the presence of twowitnesses.

JAMES G. ZIMMERMAN.

Witnesses:

CHAS. L. BYRON, Roe E. SToLL.

